1. Field of the Invention
The present invention relates to a finger strip for shielding electromagnetic wave and a front panel assembly mounting the same, and particularly to a clip-on finger strip which is located at front panels of modules inserted in the sub rack of communication facilities and is capable of preventing leakage/permeation of electromagnetic wave from/to joints between the panels, and a front panel assembly using the clip on finger strip.
2. Description of the Related Art
Nowadays, as electronic communication industries are developed and information society is established, the electric home appliances, industrial electric apparatuses and info-communication facilities are miniaturized in size. Moreover, in compliance with the request for economy of electric power, many facilities are installed in a small space, as facilities themselves are miniaturized and circuits are integrated. Accordingly, it is apt to be influenced by the noise of electric wave, and many counterplans are considered to solve this problem.
Main parts of facilities in which electromagnetic wave is easily leaked/permeated are connecting parts of the facilities, cables, transparent display plates, connectors, etc. To shield the electromagnetic wave caused by the cable, it is possible to shield the cable itself, or wire inside of the cable, i.e., core which is twisted can bc used. Moreover, to shied the electromagnetic wave which is leaked to transparent display plate, the transparent display plate is made of transparent insulated materials, or metal fabric mesh or conductive mesh is provided inside of the transparent display plate. Also, it is possible to shield the electromagnetic wave by the vacuum evaporation of the conductive material at one side of the transparent display plate.
As shown above, it is possible to shield the electromagnetic wave to some degree. However, it is not easy to shield the electromagnetic wave in the connecting parts.
In the connecting parts, shielding of the electromagnetic wave is directed to prevent electric wave generated from outside from being permeated inside of the facility through air, or to prevent the electromagnetic generated inside of the facility from being leaked outside. Though it is proper to design the connecting parts of the facility without joints to shield the electromagnetic wave, it is actually impossible not to have joints in the connecting parts. Accordingly, the permeation or leakage of the electromagnetic wave in the connecting part of the facility is inevitable, and thereby shields are provided between the joints to prevent the permeation or leakage.
Generally, in exchanges, transmission equipments, or communication facilities, when establishing a system, it is common to add modules by considering the extension possibility in the case that the demand is increased. At this time, it is important to maintain a proper interval between the modules, and to prevent the permeation or leakage of the electromagnetic wave through the joints between the modules. That is, in the case of inserting modules in the whole sub rack, when a proper interval is not maintained between the modules, modules inserted later are pressed due to the narrow space to be inserted into. Moreover, in the case of permeation or leakage caused by the absence of shields in cracks between the modules, malfunction occurs as the external devices or the extension board in sub track is influenced.
The interval between the modules is usually decided by the interval between the front panels, and the front panel generally includes a front part and side wall parts which are formed vertically at both ends. Accordingly, to establish the shields in the cracks between the front panels, it is common to locate the shield at one side wall part out of both side wall parts and to insert it into the sub rack. At this time, the height of the shield should be properly maintained to keep a proper interval between the front panels. Moreover, it is also important to provide the shield which does not easily change its shape and has a proper height, though the modules are inserted and drawn out frequently.
FIGS. 1A to 1C show an example of a conventional clip-on finger strip and fixing structure of the front panels. Referring to FIG. 1A, there is shown one part of the clip-on finger strip. Actually, a plurality of finger strips are connected to each other through common base part. Here, only one part is explained. As shown in the drawing, an elastic contact part 36 is separately extended from a base unit 32 through a first connecting part 38, and a supporting unit 34 is separately extended from the base unit 32 through a second connecting part 37.
The base unit 32, the first connecting part 38 and the supporting unit 34 are shaped like a clip, and they are designed to locate at a finger strip. Accordingly, the first connecting part 38 is operated as a spring plate having a restoring force which intends to move in a first direction. Moreover, the base unit 32, the second connecting part 37 and the elastic contact part 36 are shaped like a pincette, and they are designed to absorb shock against the external force. Accordingly, the second connecting part 37 is operated as a spring plate having a restoring force which intends to move in a second direction opposite to the direction of the first connecting part 38.
The front panels for locating the finger strip having the above-described structure are explained. The side wall part 13 of the front panel 10 includes a first part 31 having a predetermined thickness shown in FIG. 1B, a second part 33 having a thickness which is more extended from the first part, and an end part 35 having a predetermined curvature. The end part 35 has a same curvature with the first connecting part 38 of the corresponding finger strip. Also, a projection 15 is provided at the border of the front part of the front panel 10 and the side wall part 13 in the prolonged direction of the front part.
The method for shielding the electromagnetic wave using the front panel having the above-described structure and the finger strip assembly is illustrated referring to FIG. 1C. As shown in the drawing, the first connecting part 38 of the finger strip is contacted on the end part 35 of the front panel 10 and inserted into the end part 35 by pressure. At this time, the first connecting part 38 is widened and it is proceeded along the side wall part 13. As the thickness of the second part 32 of the side wall part 13 is gradually decreased, the restoring force of the first connecting part 38 is operated, and thereby the clip-shaped part of the finger strip is tightly fixed to the second part 33 of the side wall part 13. After inserting the module in which finger strips are provided at its front panels into the sub rack, adjacent modules are inserted again. At this time, the side wall part 13 in which the finger strip of adjacent module is not located is inserted, by pushing the elastic contact part 36 into a space 39 formed by the projection 15. After insertion, the restoring force by the second connecting part 37 is carried to the side wall part of the adjacent module. As a result, it is possible to have a proper interval between the modules and not to move the adjacent modules, and thereby the leakage of the electromagnetic wave between the modules is shielded.
However, the conventional clip-on finger strip has several problems. First, when the adjacent module is inserted in the sub rack, the elastic contact part is not pushed inside of the space part and it has a 180.degree. turn by the force of the inserting direction of the module. In the case that the module is inserted without sensing this state, the effect of the shielding is decreased. Moreover, although the elastic contact part is restored to the original state by sensing the present state, as the height of the elastic contact part is not the same as other elastic contact parts, the above-mentioned problem can arise in the case of inserting the module again after drawing it out. That is, when the height of the elastic contact part which is restored to the original state is lower than that of other elastic contact parts, the shielding is inefficient. On the contrary, in the case the height is larger than that of other elastic contact parts, it has a 180.degree. turn. Additionally, as this operation is repeated, the second connecting part is broken and a new finger strip should be replaced.
Second, there is a problem in that the clip-shaped part of the finger strip is slipped out of the side wall by the force of the inserting direction of the module. At this time, the elastic contact part of the finger strip is not pushed inside of the space part, and it is not lifted up. In this case, it is necessary to draw out the module and to locate the finger strip again.